Re: If cells continually regenerate, why don't tatoos go away?

Tattoos come in mostly two styles, as you already know - the temporary and 
the permanent. The temporary tattoos are just on the superficial layer of 
the skin and hence easily wear off. But the permanent tattoos are 
different. These tattoos are made by puncturing the skin and injecting the 
dye below the skin.
The skin consists of two parts - the upper superficial epidermis and the 
deeper dermis. The epidermis is constantly being worn out and replaced by 
newer cells. Essentially it is a layer of dead cells. But the dermis 
consists of living cells. It is in this layer that the tattoo ink is 
injected. Since these are living cells and not replaced as frequently as 
your epidermis, the tattoo remains permanent. And it is not that tattoos 
dont lose colour. They do fade a little. And the ink is not injected into 
the cells, but in the space between them.